target/linux/bcm27xx/patches-5.15/950-0676-i2c-bcm2835-Make-clock-stretch-timeout-configurable.patch

   1 From 8387866a1d91c78d9aa75052821b1dafa25fff0f Mon Sep 17 00:00:00 2001
   2 From: Alex Crawford <raspberrypi/linux@code.acrawford.com>
   3 Date: Fri, 28 Jan 2022 13:36:51 -0800
   4 Subject: [PATCH] i2c: bcm2835: Make clock-stretch timeout configurable
   5
   6 The default clock-stretch timeout is 35 mS, which works well for
   7 SMBus, but there are some I2C devices which can stretch the clock even
   8 longer. Rather than trying to prescribe a safe default for everyone,
   9 allow the timeout to be configured.
  10
  11 Signed-off-by: Alex Crawford <raspberrypi/linux@code.acrawford.com>
  12 ---
  13  drivers/i2c/busses/i2c-bcm2835.c | 10 +++++++---
  14  1 file changed, 7 insertions(+), 3 deletions(-)
  15
  16 --- a/drivers/i2c/busses/i2c-bcm2835.c
  17 +++ b/drivers/i2c/busses/i2c-bcm2835.c
  18 @@ -60,6 +60,10 @@ static unsigned int debug;
  19  module_param(debug, uint, 0644);
  20  MODULE_PARM_DESC(debug, "1=err, 2=isr, 3=xfer");
  21
  22 +static unsigned int clk_tout_ms = 35; /* SMBUs-recommended 35ms */
  23 +module_param(clk_tout_ms, uint, 0644);
  24 +MODULE_PARM_DESC(clk_tout_ms, "clock-stretch timeout (mS)");
  25 +
  26  #define BCM2835_DEBUG_MAX      512
  27  struct bcm2835_debug {
  28         struct i2c_msg *msg;
  29 @@ -219,12 +223,12 @@ static int clk_bcm2835_i2c_set_rate(stru
  30                            (redl << BCM2835_I2C_REDL_SHIFT));
  31
  32         /*
  33 -        * Set the clock stretch timeout to the SMBUs-recommended 35ms.
  34 +        * Set the clock stretch timeout.
  35          */
  36 -       if (rate > 0xffff*1000/35)
  37 +       if (rate > 0xffff*1000/clk_tout_ms)
  38             clk_tout = 0xffff;
  39         else
  40 -           clk_tout = 35*rate/1000;
  41 +           clk_tout = clk_tout_ms*rate/1000;
  42
  43         bcm2835_i2c_writel(div->i2c_dev, BCM2835_I2C_CLKT, clk_tout);
  44